Method for producing plastic products with reinforced heat sealed joints

ABSTRACT

A plastic product is fabricated from plastic sheets by heat sealing the plastic sheets to form an enclosure member. In order to strengthen the heat-sealed joints of the plastic sheets, the plastic sheets are thickened at portions where the heat-sealed joints are to be formed. Preferably, the heat-sealed joints are formed in such a manner that the cross-section of the heat-sealed joints is smaller than that of the thickened portions of the plastic sheet, thereby preventing effectively the non-thickened portions of the plastic sheets from being affected adversely by the heat sealing process.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a Continuation-In-Part of U.S. patent application Ser.No. 09/432,446 which was filed on Nov. 2, 1999 and which is abandoned asof the filing date of this application.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a method for producing plastic products,more particularly to a method for producing plastic products whichcomprises improvements with respect to the heat-sealing of the plasticproducts.

[0004] 2. Description of the Related Art

[0005] Conventionally, plastic products, such as inflatable cushions,air beds, floats, etc. are fabricated by joining a plurality of plasticsheet parts along the peripheries of the same. As shown in FIG. 1, thejoined portions 10, 20 of the sheet parts 1, 2 of a plastic article areheated and pressed during a heat-sealing process to form connectingseams of a plastic product. Since the thickness of the heat-sealed seamsis decreased, the structural strength at the seams of the plasticproduct is relatively weak.

[0006] In addition, to maintain a plastic product, such as an infaltablecushion pad 3, in a generally cubic configuration, connection members 31are provided within the interior of the cushion pad 3, as shown in FIG.2. The two ends of the connection members 31 are connected to twoopposed face sheets 30 of the cushion pad 3 during a heat-sealingprocess. Since the thickness of the face sheets 30 at the joints of theconnection members 31 and the face sheets 30 are decreased due to theheat-sealing process, the joints on the cushion pad 3 are liable to bedamaged when in use.

[0007] In order to address the aforesaid problems encountered with theheat-sealed joints of the conventional inflatable articles, a solutiontherefor is to use thick face sheets in fabricating products. However,this increases the costs of manufacturing such inflatable products.

[0008] U.S. Pat. No. 3,959,052 discloses a method for preparing awraparound closure for cables, pipes, splices, and junctions to effectrepair, insulation, or waterproofing. The method includes overlappingand sealing two thick edges of a sheet to form a tubular member aroundan item to be wrapped. The sheet is made of a heat shrinkable plasticmaterial. The two ends of the sheet are clamped and the material betweenthe clamped edges is stretched and cooled below the crystalline meltingpoint of the material while it is still in expanded condition. Theresulting sheet thus has a stretched central section which is heatshrinkable or heat recoverable, and two thick ends which are notstretched. These thick ends are not formed intentionally for reinforcingthe sealed joint of the two ends of the sheet. Rather, they are formedinherently when they are clamped during the stretching process of thesheet. In addition, the method in this patent provides only two thickends where the sheet is clamped. This patent does not contemplatereinforcing the heat-sealed joints of plastic products by thickeningparts of a sheet and suggests nothing relevant to the thickening of asheet in regions between two ends of the sheet.

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a method forproducing plastic products, which can provide reinforced heat-sealedjoints for the plastic products.

[0010] Another object of the invention is to provide a method forproducing plastic products, which can prevent the plastic products frombeing weakened due to a heat-sealing process.

[0011] According to one aspect of the invention, a method for producinga plastic product, comprises: forming upper and lower face sheets withmarginal parts, and providing the upper and lower face sheets with aplurality of spaced apart thick connection parts in both upper and lowerface sheets within regions confined by the marginal parts, the thickconnection parts being thicker than remaining parts of the upper andlower face sheets; and providing tension members between the upper andlower face sheets, and respectively heat-sealing two ends of the tensionmembers to the thick connection parts of the upper and lower face sheetsto form inner heat-sealed joints.

[0012] In another aspect of the present invention, a method forproducing a plastic product comprises: forming upper and lower facesheets having thick marginal parts; and heat-sealing the thick marginalparts of the upper and lower face sheets to form a marginal heat-sealedjoint by applying heat and pressure to an area, within each of the thickmarginal parts, which is smaller than the cross-section of thecorresponding one of the thick marginal parts.

[0013] In a further aspect of the invention, a method for producing aplastic product comprises: providing a plastic sheet having marginalends; thickening portions of the plastic sheet within a region confinedby the marginal ends to form thick connection parts at intervals;thickening the marginal ends to form thick marginal parts; and formingthe plastic sheet into the plastic product by heat sealing the thickmarginal parts to one another and by heat sealing the thick connectionparts to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features and advantages of the present invention willbecome apparent in the following detailed description of the preferredembodiments with reference to the accompanying drawings, of which:

[0015]FIG. 1 shows a heat-sealed joint of two plastic sheets formed viaa conventional method;

[0016]FIG. 2 shows heat-sealed joints formed in an inflatable cushionpad by heat sealing connection members to face sheets according to aconventional method;

[0017]FIG. 3 is an exploded view of an air mattress produced via apreferred embodiment of the method according to the present invention;

[0018]FIG. 4 is a perspective view of the air mattress of FIG. 3 with aportion thereof being removed;

[0019]FIG. 5 is a perspective view of a roll of sheet material formaking the air mattress;

[0020]FIG. 6 is a perspective view of another roll of sheet material formaking the air mattress;

[0021]FIG. 7 is a sectional view of an inflatable product produced byanother preferred embodiment of the method according to the presentinvention;

[0022]FIG. 8 is a perspective view of a sheet material for making theinflatable product; and

[0023]FIG. 9 is an enlarged view of an encircled portion of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Referring to FIGS. 3 and 4, an air mattress 1 produced by apreferred embodiment of the method according to the present invention isshown. The air mattress 1 is fabricated from upper and lower plasticface sheets 2, a lateral plastic sheet 3 and a plurality of plastictension members 4. Each of the upper and lower face sheets 2 has foursides and includes thick marginal parts 21 extending at the four sidesthereof, and a plurality of spaced apart thick connection parts 22formed within the region confined by the thick marginal parts 21.

[0025] The lateral sheet 3 is elongated and looped, and is formed withupper and lower thick marginal parts 31 at two opposite sides of thelateral sheet 3. The tension members 4 are disposed at intervals betweenthe upper and lower face sheets 2 and are aligned with the correspondingthick connection parts 22 of the upper and lower face sheets 2.

[0026] As shown in FIG. 5, the upper and lower face sheets 2 areobtained from a roll of sheet material 6. The sheet material 6 isembossed to define a plurality of sections 61 each corresponding indimension to the upper and lower face sheets and to form raised patterns62, 63 corresponding to the thick marginal parts 21 and the thickconnection parts 22, respectively. The sheet material 6 is cut toseparate the sections 61 that provide a plurality of upper and lowerface sheets 2.

[0027] As shown in FIG. 6, the lateral sheet 3 is obtained from a rollof sheet material 7 which is embossed to form raised patterns 71 thatcorrespond to the thick marginal parts 31 of the lateral sheet 3. Thesheet material 7 is cut longitudinally and transversely to result in aplurality of lateral sheets 3.

[0028] In order to make the air mattress 1, the tension members 4 arefirst placed between the upper and lower face sheets 2 and the twoopposite ends of the tension members 4 are connected to the respectivethick connection parts 22 via a heat-sealing process to form innerheat-sealed joints 8, as shown in FIG. 4. Afterwards, the lateral sheet3 is connected to the upper and lower face sheets 2 by heat sealing theupper thick marginal parts 31 of the lateral sheet 3 to the thickmarginal parts 21 of the upper face sheet 2 and by heat sealing thelower thick marginal parts 31 of the lateral sheet 3 to the thickmarginal parts 21 of the lower face sheet 2. As a result, marginalheat-sealed joints 9 are formed at the thick marginal parts 21, 31, andthe upper and lower sheets 2 and the lateral sheet 3 are formed into anenclosure member.

[0029] Preferably, during the heat sealing process, heat and pressureare applied to an area within each of the thick marginal parts 21, 31and each of the thick connection parts 22. Said area is smaller than thecross-section of the corresponding one of the thick marginal parts 21,31 and the thick connection parts 22. Accordingly, the cross-section ofthe heat-sealed joints 8 is smaller than that of the thick connectionparts 22, and the cross-section of the marginal heat-sealed joints 9 issmaller than that of the thick marginal parts 21, 31. To accomplishthis, the tension members 4 may be arranged to have a cross-sectionsmaller than that of the thick connection parts 22. Since heat andpressure are applied only to areas confined within the thick marginalparts 21 or 31 and the thick connection parts 22, portions of the upperand lower face sheets 2 and the lateral sheet 3 other than the thickmarginal parts 21, 31 and the thick connection parts 22 can beeffectively prevented from being affected adversely by the applied heatand pressure.

[0030] Due to the provision of thick marginal parts 21, 31 and thickconnection parts 22 in the upper and lower face sheets 2, the airmattress 1 is strengthened at the heat-sealed joints 8 and 9 and is moredurable than those produced by the conventional method.

[0031] Referring to FIGS. 7 and 8, an inflatable product 100 fabricatedby another preferred embodiment of the method according to the presentinvention is shown. As shown in FIG. 7, the inflatable product 100includes upper and lower sheet layers 101, a plurality of heat-sealedjoints 102 and 104, and a plurality of air compartments 103 each definedbetween adjacent joints 102, 104.

[0032] The inflatable product 100 may be fabricated from a sheetmaterial 110 which has a plurality of thick marginal parts 111 and thickconnection parts 112 formed in a region confined by the thick marginalparts 111. During fabrication, the sheet material 110 is folded alongline (A) and is heat-sealed along the thick marginal parts 111 and thethick connection parts 112 to form the heat-sealed joints 102, 104. Notethat the cross-section of the heat-sealed joint 102 is smaller than thatof the thick connection parts 112 as shown in FIG. 9. In other words,the areas of the thick connection parts 112 to which the sealingpressure is applied are limited within the perimeters of the thickconnection parts 112. As such, the thickness reduction occurs onlywithin the thick connection parts 112 without affecting the remainingnon-thickened parts of the sheet material, and the heat-sealed joint 102possesses a considerable strength as compared to the heat sealed jointof the conventional inflatable article which has no thickened part.

[0033] While the present invention has been described in connection withwhat is considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation so as toencompass all such modifications and equivalent arrangements.

I claim:
 1. A method for producing a plastic product, comprising:forming upper and lower face sheets with marginal parts, and providingsaid upper and lower face sheets with a plurality of spaced apart thickconnection parts in both upper and lower face sheets within regionsconfined by said marginal parts, said thick connection parts beingthicker than remaining parts of said upper and lower face sheets; andproviding tension members between said upper and lower face sheets, andrespectively heat-sealing two ends of said tension members to said thickconnection parts of said upper and lower face sheets to form innerheat-sealed joints.
 2. The method as claimed in claim 1, wherein, duringthe heat-sealing of said tension members, heat and pressure are appliedto an area within said thick connection parts, said area being smallerthan that of said thick connection parts.
 3. The method as claimed inclaim 2, wherein each of said inner heat-sealed joints has across-section smaller than that of the corresponding one of said thickconnection parts.
 4. The method as claimed in claim 2, wherein each ofsaid tension members has a cross-section smaller than that of said thickconnection parts.
 5. The method as claimed in claim 1, wherein saidupper and lower face sheets are embossed to form said thick connectionparts.
 6. The method as claimed in claim 1, further comprising:thickening said marginal parts of said upper and lower face sheets toform first thick marginal parts; forming a lateral sheet, and providingsaid lateral sheet with second thick marginal parts respectively at twoopposite sides of said lateral sheet; and providing said lateral sheetbetween said upper and lower face sheets, and respectively heat-sealingsaid second thick marginal parts of said lateral sheet to said firstthick marginal parts of said upper and lower face sheets to formmarginal heat-sealed joints.
 7. The method as claimed in claim 6,wherein, during the heat-sealing of said first and second thick marginalparts, heat and pressure are applied to an area within each of saidfirst and second thick marginal parts, said area being smaller than thecross-section of each of said first and second thick marginal parts. 8.The method as claimed in claim 7, wherein each of said marginalheat-sealed joints has a cross-section smaller than that of said firstand second thick marginal parts.
 9. The method as claimed in claim 6,wherein said upper and lower face sheets and said lateral sheet areembossed to form said first and second thick marginal parts.
 10. Themethod as claimed in claim 6, wherein each of said upper and lower facesheets has four sides, and said first thick marginal parts are formed atsaid four sides of each of said upper and lower face sheets.
 11. Amethod for producing a plastic product, comprising: forming upper andlower face sheets having thick marginal parts; and heat-sealing saidthick marginal parts of said upper and lower face sheets to form amarginal heat-sealed joint by applying heat and pressure to an areawithin each of said thick marginal parts, said area being smaller thanthe cross-section of each of said thick marginal parts.
 12. The methodas claimed in claim 11, wherein said marginal heat-sealed joint has across-section smaller than that of each of said thick marginal parts.13. The method as claimed in claim 11, wherein said upper and lowersheets are embossed to form said thick marginal parts.
 14. A method forproducing a plastic product, comprising: providing a plastic sheethaving marginal ends; thickening portions of said plastic sheet within aregion confined by said marginal ends to form thick connection parts atintervals; thickening said marginal ends to form thick marginal parts;and forming said plastic sheet into said plastic product by heat sealingsaid thick marginal parts to one another and by heat sealing said thickconnection parts to one another.
 15. The method as claimed in claim 14,wherein, during the heat sealing of said thick marginal parts and saidthick connection parts, heat and pressure are applied to an area withineach of said thick marginal parts and said thick connection parts, saidarea being smaller than the cross-section of the corresponding one ofsaid thick marginal parts and said thick connection parts.
 16. Themethod as claimed in claim 14, wherein said plastic sheet is embossed toform said thick connection parts and said thick marginal parts.